Enhanced YFV replication, despite the presence of IFN-α2, in the presence of plasma from patients with life-threatening COVID-19 and auto-Abs against IFN-α2. (A) YFV-17D replication, assessed 72 h after infection, in Huh-7.5 cells treated with IFN-α2, and in the presence of either plasma from patients with life-threatening COVID-19 and neutralizing auto-Abs against IFN-α2 (n = 8), or a commercial anti–IFN-α2 Ab, or plasma from healthy controls (n = 2). Error bars represent SEM.